This invention relates to fluid handling devices, such as microfluidic articles, including surfaces with diamond-like films thereon.
Silica capillaries are used extensively in electrophoresis, gas chromatography, electrochromatography, microbore liquid chromatography, and other chemical analytical techniques. Optical detection methods such as UV absorbance and fluorescence are often used in electrophoresis, electrochromatography, and liquid chromatography. The optical properties of silica are generally ideal for these detection methods; however, the use of pure uncoated silica capillaries is not possible because the lack of a protective coating causes the capillaries to be extremely fragile. As such, uncoated silica capillaries frequently will break under normal handling conditions.
Because of this, a protective coating must be put on the capillaries during fabrication. Conventionally, a polyimide coating is used. This coating has excellent thermal properties and gives the capillary excellent strength so that it can be easily handled; however, it is opaque and highly fluorescent and thus it is necessary to remove this coating from the portion of the capillary that is in an optical detector. Removal is somewhat difficult and it renders that portion of the capillary very delicate and easily broken.
There has also been a drive towards reducing the size of instrumentation used for analyzing and otherwise manipulating fluid samples such as biological fluid samples. The reduced size offers several advantages, including the ability to analyze very small samples, increased analytical speed, the ability to use reduced amounts of reagents, and reduced overall cost.
Various devices for microfluidic applications have been proposed. These devices typically include a glass or silicon substrate having a lithographically patterned and etched surface provided with one or more structures forming a microfluidic handling architecture. Plastic substrates such as polyimides, polyesters, and polycarbonates have been proposed as well; however, such plastic materials typically do not wet well and lack an electroosmotic flow necessary for the flow of liquid through the microchannels of the microfluidic handling architecture.
The present invention provides capillaries and other fluid handling devices, such as microfluidic articles, that include diamond-like films, preferably optically transmissive and/or hydrophilic diamond-like films. The articles of the present invention provide several advantages. For example, in the case of capillaries, optically transmissive diamond-like films do not necessarily have to be removed for detection. Hydrophilic diamond-like films provide good wetting and flow characteristics. For certain embodiments, particularly for certain microfluidic articles, the use of attachment chemistries that are used in conventional glass systems provide advantage.
The present invention provides a fluid handling device that includes a substrate and a diamond-like film (preferably one that is optically transparent and/or hydrophilic) disposed on at least a portion of the substrate. xe2x80x9cDisposedxe2x80x9d as used herein, means that the film is directly in contact with the substrate, bound or otherwise, or the film is in contact with one or more intervening layers, bound or otherwise. Herein, a film, rather than a coating, is disposed on a substrate. xe2x80x9cCoatingxe2x80x9d as used herein, generally refers to a material that is first applied to a solid substrate in a liquid state, then solidified by UV radiation (photopolymerizable), heat (thermoset), or by removing solvent molecules from the coating solution.
Preferably, the fluid handling device is a capillary having an internal surface (which is typically a fluid handling surface) and an external surface (which is typically a nonfluid handling surface), wherein at least a portion of at least one of the internal or external surfaces has an optically transmissive diamond-like film disposed thereon. Preferably, the external surface of the capillary has an optically transmissive diamond-like film disposed on at least a portion thereof.
In another preferred embodiment, the fluid handling device can be a microfluidic article having microfluidic handling architecture including a fluid handling surface with an optically transmissive and/or hydrophilic diamond-like film disposed on at least a portion thereof. xe2x80x9cMicrofluidic handling architecturexe2x80x9d includes, without limitation, open and closed or covered microchannels, reservoirs, sample handling regions and combinations thereof. The architecture may also, or alternatively, include a non-fluid handling surface having an optically transmissive and/or hydrophilic diamond-like film disposed on at least a portion thereof. Preferably, at least a portion of the fluid handling surface includes a hydrophilic diamond-like film disposed thereon.
In a preferred embodiment, a microfluidic article includes a fast polymeric substrate having a first major surface that includes a plurality of microfluidic handling architectures and a second major surface, wherein the article is in the form of a roll.
In another embodiment, the present invention provides a fluid handling device that includes a substrate and an optically transmissive and/or hydrophilic film including at least about 25 atomic percent carbon, from 0 to about 50 atomic percent silicon, and from 0 to about 50 atomic percent oxygen, on a hydrogen-free basis, disposed on at least a portion of the substrate. xe2x80x9cHydrogen-free basisxe2x80x9d refers to the atomic composition of a material as established by a method such as Electron Spectroscopy for Chemical Analysis (ESCA), which does not detect hydrogen even if large amounts are present in the thin films.
In yet another embodiment, the present invention provides a fluid handling device that includes a substrate and a film including at least about 30 atomic percent carbon, at least about 25 atomic percent silicon, and less than about 45 atomic percent oxygen, on a hydrogen-free basis, disposed on at least a portion of the substrate. Preferably, the film is optically transparent, and more preferably hydrophilic.
In still another embodiment, a fluid handling device is provided that includes a microfluidic article that includes a microfluidic handling architecture including a non-fluid handling surface wherein at least a portion thereof has disposed thereon a diamond-like film that is optically transmissive, hydrophilic, or both.
The present invention provides a method of manufacturing a hydrophilic diamond-like film. The method includes treating a diamond-like film in an oxygen-containing plasma
Various other features and advantages of the present invention should become readily apparent with reference to the following detailed description, examples, claims and appended drawings.
The present invention provides capillaries and microfluidic articles, as well as other fluid handling devices, and methods of manufacturing the same. For purposes of this invention, the following definitions shall have the meanings set forth.
xe2x80x9cAxe2x80x9d or xe2x80x9canxe2x80x9d refers to one or more of the recited elements.
xe2x80x9cAffixxe2x80x9d shall include any mode of attaching reactants to a diamond-like film. Such modes shall include, without limitation, covalent and ionic bonding, adherence, such as with an adhesive, physical entrapment, and adsorption. This may or may not require the use of linking agents.
xe2x80x9cAnalytexe2x80x9d shall mean a molecule, compound, composition or complex, either naturally occurring or synthesized, to be detected or measured in or separated from a sample of interest. Analytes include, without limitation, proteins, peptides, fatty acids, nucleic acids, carbohydrates, hormones, steroids, lipids, vitamins, bacteria, viruses, pharmaceuticals, and metabolites.
xe2x80x9cDiamond-like filmxe2x80x9d refers to substantially or completely amorphous films including carbon, and optionally including one or more additional components selected from the group of hydrogen, nitrogen, oxygen, fluorine, silicon, sulfur, titanium, and copper. Other elements may be present in certain embodiments. The films may be covalently bonded in a random system or in an interpenetrating system, such as in an interpenetrating diamond-like nanocomposite (called DYLYN), as described, e.g., U.S. Pat. No. 5,466,431. The amorphous diamond-like films of this invention may contain clustering of atoms that give it a short-range order but are essentially void of medium and long range ordering that lead to micro or macro crystallinity which can adversely scatter actinic radiation having wavelengths of from 180 nm to 800 nm. The term xe2x80x9camorphousxe2x80x9d means a substantially randomly-ordered non-crystalline material having no x-ray diffraction peaks or modest x-ray diffraction peaks. When atomic clustering is present, it typically occurs over dimensions that are small compared to the wavelength of radiation.
xe2x80x9cHydrophilicxe2x80x9d as it relates to a diamond-like film shall mean a diamond-like film having a water contact angle of about 50 degrees or less, and preferably about 30 degrees or less.
xe2x80x9cLinking agentxe2x80x9d shall mean any chemical species capable of affixing a xe2x80x9cReactantxe2x80x9d to the diamond-like film. Linking agents can be covalently bonded to the diamond-like film or provided by a polymeric coating thereon.
xe2x80x9cOptically transmissivexe2x80x9d as it relates to a film refers to the film having an extinction coefficient of no greater than 0.3 at 500 nanometers (nm). Preferably, the extinction coefficient is no greater than 0.010 at 250 nm.
xe2x80x9cReactantxe2x80x9d shall mean any chemical molecule, compound, composition or complex, either naturally occurring or synthesized, that is capable of binding an analyte in a sample of interest either alone or in conjunction with a molecule or compound that assists in binding the analyte to the diamond-like film, such as, for example, a coenzyme. The reactants of the present invention are useful for chemical or biochemical measurement, detection or separation. Accordingly, the term xe2x80x9cReactantxe2x80x9d specifically excludes molecules, compounds, compositions or complexes, such as ink, that do not bind analytes as described above. Examples of reactants include, without limitation, polypeptides (e.g., proteins such as enzymes and antibodies), polynucleotides (e.g., oligonucleotides and cDNA), and carbohydrates.